154 STURGEONS. 



his journey into Siberia, mentions an example, of only six 

 feet long, the roe of which measured two quarts; and another 

 is recorded, that weighed two hundred and seventy-three 

 pounds, the roe of which amounted to forty-two pounds, the 

 supposed number being almost two millions. It is not there- 

 fore in purses, or by internal hatching, that the young are 

 produced to life, but more strictly in the manner of bony 

 fishes, the grains being, however, rather large, and separated 

 from each other throughout the mass by layers of fat. It is 

 one of the principal objects of the Russian fisheries to obtain 

 this roe, which is carefully prepared, and valued by epicures 

 under the name of Caviare. 



Another valuable product of this fishery, and of more general 

 importance, is isinglass; which is formed of the air-bladders 

 of two or three species of this genus, and of which, one of 

 the smaller kinds, (A. ruthenus,) is said to produce the best. 

 The organ from which it is prepared is not found in any other 

 of the plagiostomous genera, Sharks or Skates; but in the family 

 of Sturgeons it appears to be of great use in enabling the 

 fish to rise and fall frequently and rapidly amid the currents 

 of the larger rivers, as well as in the deeper waters of the 

 sea. The structure of this organ has a remarkable peculiarity, 

 in the existence of a duct or passage of no small size, which 

 passes from the bag to the gullet, and by which the air within 

 may be occasionally discharged, and perhaps again renewed 

 from without; for we are not able to affirm positively what is 

 the special or complicated object of a structure which is only 

 shared by a few of the fishes furnished with an air-bladder. 

 In an example of the Common Sturgeon, of about eight feet 

 in length, which I knew caught in a trammel in the open 

 sea, as the fish was raised from the ground some observable 

 bubbles of air were seen to break from the water; and I 

 have no doubt they had been discharged from the fish, perhaps 

 under the influence of the terror produced by its capture. 



Isinglass was known in ancient times . by the name of 

 ichthyocolla, or fish-glue, and it was used in the medical 

 practice of Greece and Rome as a principal ingredient of 

 their adhesive plaisters; but the fishes which produced it 

 were on another account a subject of attention to the Romans 

 of the flourishing times of the empire. 



